Michigan Bluff, CA. May 20, 2012. It’s day two of Michigan Bluff Training Camp – the annual Western States training week. Relaxing in Carol’s house on the corner of Michigan Bluff Road and…the Western States Trail, I lazily pull out a rather thick, heavy paperback nestled deep the backpack, adjacent Seinfeld and The Office DVD sets. The DVDs beckon, but the book intrigues.

I opened. I read. And read. I couldn’t put it down.

I plowed through Waterlogged (initial iRF Waterlogged review and discussion) and, as soon as the words lifted off the page, I began talking the ears off of veteran ultrarunners Craig Thornley and Meghan Arbogast, me with the passion and giddiness of scientist having a “eureka!” moment.

“Have we been off base? I have I been doing it all wrong?” I wondered.

After that first night, I began the Experiment of One, applying Noakes’ recommendations to the T:

Drink to thirst

No salt

Steady stream of sugar

And I felt great. I ran nearly two hundred miles over those seven days, including 48-mile effort from Robinson Flat to the River on the last day of camp. Besides a half-a-pastrami sandwich and a Pepsi, I had only gels and water.

I was ready. But could I really go with less water, more sugar and…gasp…no salt?

I need more answers. Two weeks before WS, I went straight to the source. I sought out Dr. Noakes, himself:

Q&A with Tim Noakes, MD

iRunFar: You noted that, in the vast majority of cases, additional sodium supplementation is unnecessary – outside of “daily intake.” Given that most folks ingest more than 5 grams of sodium per day in a “typical Western diet,” what do you recommend for supplemental sodium in all-day races, such as Western States 100, that take 16-30 hours?

Tim Noakes: No need to take anything since the body starts with the excess from the previous day’s intake and is in the process of excreting it during the race. Adding any additional sodium simply increases the load that the body must get rid of.

iRF: What are your thoughts on the notion that one must maintain internal fluid volume to sustain blood circulatory volume? Do weight loss percentages beyond the previously accepted 2% have any effect on blood volumes or blood pressure?

Noakes: The key question is whether those losses impair performance, not what they do to the circulation. We routinely measure weight losses in excess of 10% in winners of marathon and ultramarathon races. I do not see any evidence that weight losses in excess of 2% impair performance. Rather I suspect that this degree of weight loss is beneficial since it lightens the load that must be carried.

iRF: Rhabdomyolysis and renal failure are prominent concerns with 100-mile ultrarunners, with several notable cases over the past five years in the sport. What does the research or current medical theory state is the primary cause of “rhabdo?” How does hydration and electrolyte levels possibly impact rhabdo? What about NSAIDs?

Noakes: Rhabdo has to be due to a genetic disorder since it occurs so infrequently. Since everyone loses weight and electrolytes and many ingest NSAIDs without developing rhabdo, the cause has to be something else. Certainly hydration has never been shown to have anything to do with the condition. People lost in the desert die from kidney failure without rhabdo (as far as I know).

iRF: There’s a belief out there that one must drink copious fluids and “pee a lot” to ensure ongoing kidney function during and after long ultramarathon efforts. What, if anything, can runners do to ensure they’ve got well-functioning kidneys during competition?

Noakes: We showed already in the 1980s that the kidneys are barely affected by running marathons. The effort is so submaximal that the kidneys are in no distress. So there is nothing that has to be done to keep the kidneys working during a marathon – other than to drink to thirst.

iRF: You noted a “cultural difference” regarding hydration and salt supplementation amongst California-based ultramarathon races. Can you expand more on that – those differences between ultra races in other parts of the world with similar climates and conditions – and what could be done differently in those races to ensure optimum performance and health?

Noakes: South Africa and New Zealand runners have been warned since the early 1990s of the dangers of overdrinking. But in the US, the sports drink industry drove a different agenda and wanted runners to drink as much of their product as was possible. As a result US runners were conned to believe that if they did not drink “as much as tolerable” they would at best have a poor race and at worst die from dehydration. Instead, this advice caused an epidemic of hyponatremia and poor performances since we now know that athletes who drink ahead of their thirst impair their exercise performance.

iRF: The research studies cited in your book find little to no impact of hydration on core body temperature. What advice could you give ultrarunners in mitigating heat stress while maintaining consistent running performance, especially in hot weather 100-mile races over rugged terrain?

Noakes: The core temperature response to exercise is determined by the rate of doing work – that is the speed at which you run. The running speed is so slow (relative to maximum capacity) during a 100-mile race that the core temperature will be low in such races. So there is no need to do anything other than running at the speed that your body tells you to run at.

iRF: You also touched briefly on the association between hyponatremia and muscle cell breakdown (as measured by creatine phosphokinase blood levels). Can you expand more on that, what the research has found, and what the current theory is relating the two?

Noakes: It does appear that there is a link between hyponatremia and muscle cell breakdown. Why this happens is still not known.

iRF: Races such as Western States 100-mile have medical checkpoints, where runners check-in with medical personnel and, among subjective questioning, submit to weigh-ins, comparing pre-race weight to current. Given the research findings that dehydration does not significantly impact core temperature, and that certain levels of dehydration appear to be optimal, what should both competitors and medical staff, alike, be monitoring at medical checkpoints?

Noakes: The only variable that one must avoid is a gain of weight. All else is not particularly helpful. A recent study found that runners who lost significant weight were more likely to finish than those who loss less weight. The blood pressure measurements are also not particularly helpful. Provided the athlete is able to run, has no symptoms and is not confused, I would let them continue.

My Experimental Western States Plan

There it was, laid out plainly:

Drink to thirst; I don’t need water to maintain temperature, circulatory volume, or kidney function.

Take no salt; we simply don’t need it to maintain blood sodium levels.

Get steady sugar; the one true performance-enhancer.

The plan for Western States was this:

Hydration packs. The tipping point to using hydration packs instead of conventional hand-held bottles was this interesting notion: when we have something in our hands, we tend to consume it, regardless of need. Think about being in a tavern, beer in hand: do you drink it because you’re thirsty, or because it’s there? What about that bowl of candy on the desk in your office? In order to truly drink to thirst, I figured having water readily available – but not in hand – would rule out that drink-in-hand psychology.

Steady stream of sugar. Noakes recommends 60g (to upwards of 100g) of sugar per hour. That’s 3 gels an hour, solid. Knowing I’d be out there all day, and likely running harder than I’ve ever run, I set a repeating watch timer for every 19 minutes, with the intent on taking a full gel with each interval.

Salt-free. I was most uneasy about this. Sure, it worked in training. And it’s tough to argue 30 out of 31 studies showing increases in blood sodium across marathon and ultrarunners who simply drink to thirst and don’t supplement. Even tougher to argue the foremost authority in hydration research in the world! But I’ve been a salt addict. My plan was to take none, but – being the de facto Boy Scout that I am – I was prepared with a small cache of 3 S-Caps in each hydration pack…just in case.

My Western States Reality

Western States 2012 was a race to remember for many, myself included. I ran hard, but conservative through the high country into Robinson Flat (mile 30), sticking to the plan. However, running the flat from Miller’s to Dusty Corners (mile 38) – I felt…”down.” Not cramping, not dead-leg, just…down. I felt off, mentally, and my legs had no pop. I was running 8-minute miles on a section where the ten guys in front of me were running sub-sevens. I was drinking to thirst, I’d eaten a lot (two PB&Js and a candy bar in the last 7 miles). What gives?

I’d been running for five hours, hard. No salt.

Damn.

I reached into the hydration pack to find my mini-pouch of S-caps. I bit down. It tasted good.

With the next thirty minutes, two interesting things happened: My brain and legs returned to life, and my stomach felt much better. I took a second S-cap just before Last Chance (mile 43) and within two miles felt the strongest I’d felt since the first hour of the race.

For the rest of the race, I took an S-Cap about every 45-60 minutes. I continued to drink to thirst and maintain steady sugar intake.

As my race report – and race results – has pointed out, I had a good day. Compared to my 2011 WS race, when any amount of fluid or salt was repulsive, it was a great feeling to run hard in the last twenty miles and have water “taste good.” In the last ten miles, I increased my gel intake to four per hour. The majority of my fluid came from washing down gels and the odd soda at aid stations.

After finishing, my blood sodium was 140 mmol – in the meat of the normal range.

To review:

Drinking to thirst. Worked incredibly well. I drank only when I felt like it – or when I was washing down fuel. Indeed, Noakes talks about natural rehydration, and how it is always accompanied by food – not necessarily salt. Thus, I felt it worked excellent to take in fluid when I was ingesting food.

Sugar. My three gels an hour was effective, but I neglected to take solid food early. I feel some bananas or breads early would have prevented some GI rebellion in the middle miles.

Salt. Tough one. I went 37 miles and more than 5 hours with no salt. But that mental and physical “down” I experienced – that was gradually improved with sodium intake – is difficult to explain. Devil’s Advocate: Was it placebo effect that I felt better? Was it because I slowed down, that my body naturally rebounded? Or is there an alternate avenue by which sodium provides real physiological benefit?

The Salt Mystery

So, where do we stand with salt? I wanted to believe it wasn’t needed. I tried. But I used it, and – as scores of iRunFar commenters argued – it helped.

I went back to Dr. Noakes with more questions:

Tim Noakes (on why hyponatremia rates have fallen the past two years at WS): First, I suspect that runners are now drinking less in the Western States and that is the reason why the incidence of EAH is falling as you clearly also conclude.

iRunFar: Besides a pure placebo effect, might there be another mechanism (neurological, neuromuscular) by which we gain benefit from ingesting salt? Has that been examined as of yet?

Noakes: Biologically, there is no reason to suspect that it works by preventing sodium deficiency, since it is not possible to become sodium deficient even in the Western States race. There is this additional store of sodium that we access when required. The low incidence of EAH in ultradistance events (historically and in races like those in South Africa and New Zealand where overdrinking is not promoted) even when sodium is not ingested shows that sodium deficiency is not a common feature.

Thus I would conclude that if sodium ingestion improves performance it is working in a way that is unrelated to the reversal or prevention of a sodium deficit.

However, it is clear that sodium has a major stimulatory effect in the brain as shown by the sodium ingestion (pickle juice) breaking the cramps study discussed in Waterlogged.

So I would argue that if salt ingestion does improve performance, then it is by a centrally acting brain effect that is different from a placebo effect. Of course, there may also be a placebo effect, as well.

There are studies showing that sodium ingestion improves performance – studies coming out of New Zealand. They need to be repeated. We did not ever study the performance effects of sodium ingestion – only the physiological effects and we found those to be disappointing. We need more studies of this possible effect.

So, yes, there may definitely be another mechanism by which sodium ingestion could affect performance acutely – i.e., within minutes of ingestion – and that would most likely be a central brain effect much as glucose ingestion does the same. Interestingly salt, fat and sugar are the three addictive foodstuffs and that may be the link to acute changes in performance when they are ingested.

Those statements were reassuring to read: that salt may work…but we just don’t know why. Yet.

Hyponatremia and Western States – Past, Present, and Future

I was pleased with my effort at Western States, and the newfound knowledge I gained from Waterlogged. However, in a sport where community means more than any other, I was driven to be sure that everyone – from M1 to 29:59 – was armed with this information.

Dr. Noakes called out “Northern California Ultramarathons” as being ground zero for the hyponatremia problem: both Western States and Rio Del Lago were cited with hyponatremia rates in excess of 30% (Rio, in 2008, had an incredible 50% rate).

Is this uniquely a “Northern California” problem? Unlikely. It’s simply that the vast majority of all ultramarathon research comes from Western States. A survey of other hundreds – namely those in warmer climes – might find similar numbers.

Given the alarmingly high rates of hyponatremia found there, I was driven to know what the Western States Endurance Run was doing to with this information, and how they are addressing their own issues with hyponatremia.

Q&A with Dr. Marty Hoffman, Director of Medical Research, WSER

iRunFar: When did research and testing start at the WSER, and who or what was the impetus for it?

Marty Hoffman, MD: The WSER has a long history of scientific inquiry that began with the interests of Dr. Bob Lind [the first medical director of WSER]. Unfortunately, much of the early work did not end up in scientific publications. It was around 2002 when aggressive scientific work began, and, by 2006, we started to see a number of scientific publications arise from work performed at the event. Following the 2005 event in which I performed some pain perception research, I suggested a more formal research program at the WSER to oversee and promote the process. By the 2006 WSER, we had in place a mechanism for funding research at the event and a research committee composed of an international group of scientists to review proposed studies. Part of the mission of this program was also to assure that research performed at the event would likely contribute to our scientific knowledge, and that mechanisms would be developed to return this new information to the runners. Since that time, research at the WSER has accounted for approximately half of all scientific papers related to ultramarathon running.

I became interested in investigating exercise-associated hyponatremia largely from Brian Morrison’s hyponatremia incident at the 2006 WSER. Our initial study was planned for the 2008 WSER, but you will recall that that was the year the race was cancelled due to nearby fires. It turns out that our initial study was actually performed later in the year at the Rio Del Lago. Earlier in 2008, Dr. Tim Noakes had connected me with Dr. Tami Hew-Butler, one of his former doctoral students who had returned to the United States. I invited her to the 2008 WSER to see the event, and with the intent that she would subsequently organize some studies in future years. She didn’t get to see a race, but she got a feel for the event, and for the 2009 WSER, she organized an international team of investigators. We’ve basically been collaborating since. Much of the work of this group has been related to exercise-associated hyponatremia, but we have also been examining fluid and nutritional requirements, rhabdomyolysis and acute kidney injury. We have other research groups and collaborators that have been examining characteristics of ultramarathon participants, cardiac function in ultramarathoners and foot strike pattern during ultramarathons.

Hoffman: It seems that 100-mile ultramarathons in northern California are the mecca for exercise-associated hyponatremia as we’ve found much higher rates in our studies at these events than has been observed anywhere else in the world. In our initial study at the 2008 Rio Del Lago, we found that 51% of the study participants had exercise-associated hyponatremia at the finish. Then, at both the 2009 and 2010 WSER, rates were 30%. Interestingly, the 2011 and 2012 events have had much lower rates of 6% and 5%, respectively. An obvious question is why have the rates been lower the last two years? Certainly the cooler ambient temperature conditions may have played a role. We would also like to think that our educational efforts may have had an impact, as well.

iRF: Your WSER research team has published some thought-provoking studies in the past three years. Findings that come to mind include your studies of the ’08 Rio Del Lago 100 and the ’09 WSER that concluded that changes in weight cannot predict hyponatremia, and the study on the relative effectiveness of treating hyponatremia with a 100mL IV versus oral salt. How much do your research findings, or the data you collect each year affect the medical recommendations for the Run?

Hoffman: Indeed, because of our research, the medical guidelines at the WSER have been adjusted. The work of Dr. Noakes and his colleagues has shown that one is more likely to develop exercise-associate hyponatremia when there is weight gain. Interestingly, this is not the case in our environment. For instance, our work has shown that roughly a third of runners who are hyponatremic at the finish have lost over 3% of their body weight, and only about 20% have gained weight. As such, weight change appears to be of little value in determining who might be likely to be hyponatremic. Besides our work related to hyponatremia, we’ve also observed that some of the top runners lose more than 5% of their body weight without evidence of issues. So, for the 2010 event, we completely removed from the weight change guidelines any criteria for holding a runner based upon weight change. These guidelines provided to the medical and aid station staff basically specify that weight loss of up to 3-5% is appropriate, less than this should trigger a recommendation to consider reducing fluid and sodium intake, and more than this should trigger a recommendation to consider increasing fluid intake, and possibly sodium intake, as well.

Our efforts have also resulted in some changes in our medical treatment at the WSER. There have been several reports of hyponatremic marathon runners dying after being treated with IV normal saline. Actually, it’s been more than a couple decades since we’ve had some evidence that such treatment can be disastrous. Unfortunately, even now there are still some places where the usual treatment for exercise-associated hyponatremia is isotonic saline. Fortunately, there have not been any deaths of ultramarathon runners from such treatment as far as I am aware, but I think that simply means that we’ve been lucky so far.

The proper acute management of symptomatic exercise-associated hyponatremia is now known to be a small bolus of hypertonic saline, either IV or orally. Our treatment trials at the 2009 and 2010 WSER contributed to this knowledge. As a result of this information, we now have guidelines at the WSER that runners are not to be given large volumes of IV fluids without knowledge of their blood sodium concentration. We also now have hypertonic saline available for proper management of exercise-associated hyponatremia.

Q&A with Kerry Sullivan, MD – Medical Director, WSER

iRF: What does the WSER recommend for runners looking to avoid either dehydration or over-hydration and hyponatremia?

Kerry Sullivan: WSER currently recommends: Drink to thirst using the electrolyte drink of your choice. The Race provides Gu2O along the course.

iRF: In the 2012 WSER, there was a notable case on a runner held at an aid station for over two hours due to apparent weight gain of less than 5%. Does the WSER have standardized guidelines that medical captains must follow to determine when to hold, release or pull a runner from the race? If so, what are those guidelines?

Sullivan: WSER relies on clinical acumen, rather than absolute weight gain or loss, when deciding whether to recommend that a runner sit for a while. When a runner looks unwell or their weight is significantly up or down, we encourage a runner to rest and recoup, not drop. We know from experience that a period of rest usually improves their status, making it safer for them to continue on.

iRF: In Dr. Noakes’ book, he discusses how hyponatremia is commonly misdiagnosed – either as dehydration or heat stress – and mistreated – typically by administering hypotonic IV fluids. What criteria do WSER and its medical captains use to diagnose hyponatremia, and what methods do they use to treat it?

Sullivan: Marty [Hoffman]’s data have been invaluable with respect to hyponatremia. We start with medical evaluation of the runner – are they mentating, urinating, vomiting, edematous, weak, et cetera. We keep hyponatremia in mind. If a runner looks unwell, we no longer assume it is simple dehydration. We are judicious in our use of hypotonic IV solutions. At the finish line we have an i-Stat to check the sodium. If the sodium is low and the runner is having extreme symptoms (changes in mentation), we would start an IV of hypertonic saline and arrange ambulance transport to the ER.

Leading the Charge: Western States as the Leader in Best Fueling Practices

Western States is regarded highly as the grandfather of hundred mile races, the de facto national (if not world) championship hundred, and a leader in ultramarathon racing. Commensurate with that reputation, Western States needs to be at the forefront of this latest research.

More importantly, it needs to adopt a consistent message. Throughout the Western States website, there are conflicting messages regarding nutrition recommendations.

My recommendations for the Western States Endurance Run:

1.) Adopt and profligate the findings of Noakes, Hoffman, et al. regarding the role of water, sodium and fuel, namely:

The role of sodium is so far unknown. Take sparingly. Do not expect it to solve all your problems: research has shown it does not aid in performance, nor does it prevent hyponatremia.

The only prevention of hyponatremia is to drink to thirst and avoid excessive fluid intake.

It is unnecessary to push fluids beyond thirst – before, during, or after the race.

2.) Prioritize the medical risks, from highest to lowest.

Western States puts significant emphasis on two medical events that occur with incredible rarity: heat illness and kidney failure.

The false belief that hydration prevents heat illness is so strong that it drives people to drink more than they need. Heat management is important, but orders of magnitude less than believed.

According to Noakes’ research, heat stroke (measured by a core temperature over 41C) has been documented only six times in the past hundred years in events of marathon or longer. Six. In a hundred years. It’s likely been wrongly diagnosed (along with “the nondisease of dehydration,” as Noakes calls it), thousands of times.

Kidney failure – defined as a measurable loss of kidney filtration rate – is also extraordinarily rare: on the order of 1% per year, or less. According to Hoffman’s findings, it is largely associated with inadequate training, running to fast, and NSAID use. Hydration, so long as one is drinking to thirst, has no effect on the incidence of kidney failure. Rhabdomyolysis might.

To our knowledge, no one has ever suffered full and permanent kidney failure as a result of running an ultramarathon,

Prioritize hyponatremia: given that it is found at 4-6% rates at best – and up to 50% at its worst – this medical condition should be emphasized most strongly: at best it will ruin your race; at worst, it can kill you.

Implore runners to drink only to thirst, to avoid drinking any fluid to excess or beyond thirst, and warn them of the signs and symptoms, and the consequences, of hyponatremia.

3.) De-emphasize post-race fluid-pushing.

Throughout the website and the participant guide, it states that runners should “continue hydrating for several days until urine is light yellow and normal frequency.”

To reiterate: according to the bulk of research, neither urine frequency nor color indicates kidney function. A simple recommendation of “drink to thirst” is all that is needed.

Indeed, Noakes noted that most of our rehydration occurs when we ingest food. Given the intense demands on the metabolic systems, a recommendation of “ingest calories as soon as possible following the Run” will ensure glycogen restoration, along with typical dietary fluid intake that naturally goes along with that food.

What We [Probably] Know – The Take-Home Lessons

Through it all, here is what the lessons of Waterlogged, and a decade-plus of research at Western States, have shown us:

Drink to thirst! Drink to thirst! If seventy years of research, and a 400+ page review of it by Tim Noakes in Waterlogged, can be distilled to three words, those are it. Don’t fear dehydration. Even if you become deficient enough to impair performance, water is quickly absorbed and any ill effects are short-lived. But over-hydrating can take hours – or days – to reverse. Drink to thirst!

Keep the stomach turned on and the calories streaming.Food is one substance that the body easily deals with in excess (the obesity epidemic is ample proof of that). Individualize: eat what works for you. Unlike water (and salt), carbohydrates are much slower acting and, when in deficit, can be very slow to replace. Keep the calories flowing!

Salt probably helps – we just don’t know why. It’s not because of blood sodium. But as Dr. Noakes theorizes, there might be a brain or neurological action wherein salt improves performance. We just don’t know for sure yet.

Be minimalist, especially with the things the body doesn’t easily handle: water and salt. Most of us train with minimal salt and water, even on long runs. Thus, it doesn’t make sense to radically and regimentally increase these things in an ultra. Listen to your body!

I hope these works have been as impactful and helpful to you as they have for me. Use science to fuel your passions, but never stop that “experiment of one.”

Call for Comments (from Bryon)

Discuss.

[Disclaimer: The contents of this column as well as the author’s comments are provided for general informational purposes only and are not intended as a substitute for professional medical advice. Do not use the information on this website for diagnosing or treating any medical or health condition.]

Joe Uhan is a physical therapist, coach and ultrarunner in Eugene, Oregon. He is a Minnesota native and has been a competitive runner for over 18 years. He has a Master's Degree in Kinesiology, a Doctorate in Physical Therapy, and is a USATF Level I and II Certified Coach. Joe ran his first ultra at Autumn Leaves 50/50 in October 2010, was the bronze medalist at the 2012 USATF 100K Trail Championships, and finished M9 at the 2012 Western States 100. Joe works at Eugene Physical Therapy in Eugene, Oregon, and offers online coaching and gait analysis at joeuhan.blogspot.com.All posts by Joe Uhan

I've just read waterlogged and have been experimenting myself as it seems to make sense.

Drinking to thirst seems to work for me, I just don't think I'm taking enough carbs, but I'm not sure if I should be taking 3 gels per hour (as you did) as I'm not the fastest runner, did you take 3 "every" hour during the 100 and did you have any carbs in your drinks or just pure water?

Thanks for the comment. I took gels on a repeating watch timer every 19 minutes, nearly without fail (though my stomach did rebel for a middle patch). From mile 88 to the finish, I took them every 15 minutes.

Oddly, I ate very little solid food. In hindsight, I wish I'd eaten more bananas/potatoes, as they tend to be easily digestible and tend to "level out" the stomach.

Pure water in my pack. Did drink soda in the last 30ish miles. Took no Gu2O or any other sugared/salted drink.

also, thanks for pursuing your inquiry on this subject. Hydration and electrolyte replacement are areas of uncertainty for lots of us, and personally I have not yet found an approach that works for me in 50-100 mile races. I'm excited to try to a less salt-forward approach at Wasatch in a few weeks; in my only other attempt at 100 miles, I ran well until ~mile 80, when I experienced extremely painful bloating, and a subsequent loss of energy. I have been wondering if perhaps my sodium/electrolyte routine, which I continued all night and to which I added frequent cups of broth after ~65 miles, caused me these problems.

So far, I haven't had an s-cap since june, and I haven't had any issues. Thanks again.

As stated above, I do feel sodium is helpful, but to be used as sparingly as possible…and with as little fluid as possible. It seems the best way for the body to go "haywire" is to have a ton of fluid…and salt…on board at once…

Since I have not read the Noakes book – This info is helpful. I am still struggling with the information seems to be applied to 100% of all runners. Maybe it is true for all – If not will some people put themselves as risk?

I am a heavy sweater – At easy pace for 10 miles on a (70F / 60% humidity) Typical WI summer morning I will lose 7-8#

In a recent 24 hour race I lost 14 pounds in 12 hours while drinking 4 gallons of water between straight water and mixing with fuel. It was mid 70s not overly warm. During this time I think I urniated once. I did not wait to drink to thirst, if I had the perception is the weight loss would have been significantly more. I am aware that I was losing some glycogen and other weight than just hydration – But at 24 hour pace it was also hydration.

On 4-6 hour runs if I wait to drink to thirst (I have tested it 4-5 times now) I end up cooked.

Although there is a lot of "Truthism" in the book – Is it true for 100%?

Will some people end up too dehdrated from the book – Face serious medical issues including possibility of death?

How do you eat 3 gels an hour for 30 hours? (90 gels!!!)Is it electrolytes and/or water to drink to thirst? Like many others I pop an S-cap for insurance but prefer solids if possible. I always thought cramp meant lack of salt….perhaps I'm behind the curve.

60-100g of sugar an hour does not imply only gels — it can be any carbohydrate. Gels are obviously more convenient, but I know runners who carry bags of gummy bears for the same convenience and carb density.

Phil, feel free to consult Part I of the review – or Dr Noakes' book – and its discussion on salt with cramping, where the current research shows no association between cramp relief and sodium.

Wow, such good timing with this article, and what an excellent piece. I have been trying to figure out my own hydration over the past weeks. I have found that I drink FAR less than most and my performance has not degraded at all. I was thinking that maybe I was doing it wrong, but maybe not…

Thank you so much, Joe, for your insights on Dr. Noakes's book and for the follow up with Dr Noakes! I am reading the book at the moment myself, but it really helps to have your analysis – so intelligent and yet accessible. I have always believed in drinking to thirst but at times wondered if I should take s-caps of some such durings ultras, but never really tried. I do, however, eat salty snakcs at aid stations when I crave them – so it seems a little more organic, kind of like, listening to your body – drinking when the body is asking for it (thirsty)and eating salty food when they look appetizing (craving salty things).

Thanks so much again, Joe for such thorough and candid insights on a very important topic.

It's a freightening subject because it's body chemistry but it's good that people are talking about it. I'm weary of comparing Front runners (those that participate in the studies) with "Back of the Packers".

Great follow-up article. My thirst seems to come and go while training when I'm taking meds for alergies. Can we augment a faulty thirst drive with a lack of urination metric? Any idea on how many folks out there have a faulty thirst drive while taking meds for alergies? Thanks!

Joe, great article. having read the book and had Rhabo/196,000 CPK after WS2010 (as you might remember) this is an issue I've looked into abit. I agree completely with your recomendations… Water to thirst and very easy on the salt. Thanks for doing the homework.

I really like this article. It brings up a long standing point for me – that science doesn't always have the answers and that doctors simply "practice" medicine. Similary, I practice ultramarathons and I still don't know that I'm doing – but I love it! Every day is still an experiment. Like Michael shared earlier, I too sweat heavily. In many of my 50 k.m. races I will be ~10 lbs. lighter at the finish line, usually that is a painful state for me to be in – I weigh 178-180 lbs. at most race start lines. Nausea is normally what takes me out of races and/or has me feeling like crap at a finish line. I've been told that nausea is caused from either dehydration or low blood sugar levels. In my feeling-at-my-best race finishes, I usually have only lost ~2-3 lbs. over an ultra distance. At WS100 this year, I only lost ~1-2 lbs. on average for the 70.7 miles I completed, but still experienced nausea, beginning at mile 31.

What I do know for certain, is that my pace/effort level is the main driving factor in my ability to complete an ultra distance. Simply put, my gut shuts down istantly and my core tempature rises when I push super hard. Fluids can go in my gut, but don't absorb. So it is possible for me to drink a ton of fluids, but still be dehydrated, because the fluid is stuck in a cement bowl (my stomach).

I have experimented for a couple years with hydration techniques and salt. I have found that I can run up to about 20 k.m., at a fast pace/effort level, without taking any fluids/salt and be mostly okay after (temperature playing a factor) and just thirsty. But I start playing mind games with myself thinking "oh my gosh, I'm going to die, if I can't get some water, NOW". Keeping 2-4 ginger (Gin Gin Boost) candies in my mouth, keeps the saliva flowing and tricks my mind into thinking I don't need fluid. I don't recommend this, but I sometimes need to experiment with self inflicted dehydration, or a small degree of it, to really know what it feels like, on its own, compared to over eating/hydrating and getting a bloated stomach and getting bad nausea. Pracatice makes perfect, some day!

Salt: I have experienced the beginning onset of cramping in my legs during an ultra, I took sodium (s-caps) and the cramping disappeared. I have also had cramping and then shaken my legs vigorously and the cramping went away, at least to go 1/2 mile to a finish line. When I under-salt (no specific sodium supplimentation during a long run/race) and get dehydrated, the muscles in my feet often will spasm/cramp, if I stretch or bend my toes that night in bed – taking sodium takes that away, within 5-30 minutes. I also "think" (still experimenting here) that sodium helps my stomach absorb fluids better.

I still fear anyone who takes on this advice for a hundred miler. When every Joe asks a question about a 100 mile distance, Tim refers back to Marathons. We get it, we no longer live in the 80's when hyponatremia was the situation.

So no salt need for a Marathon; got it.

Excelent point Joe makes on consuming to much salt in the begining and taking in solid foods for the sake of not having to deal with gue and possibly an upset stomach in the end.

Salt is essential for a 100 miler. And Kilian should have been DQ'd from the Speedgoat 50k. These are the only two things I know for certain in life. FYI, I just watched the Tetons video of Anton and Kilian and both guys are awesome. Again, nothing personal. But people need salt after 20 hours in the mountains (hell I like pretzels after a walk around the block), and runners all need to follow the same rules in races. Again, the only 2 truths in life.

Thanks for summing up (and now I don't have to really buy and read the book unless need more info). Obviously, we are all an experiment of one, but there got to be something general. I never use salt in training, and used to not drink a lot until I moved to TX (from OR). With salt, first year or so I wasn't taking any beyond a can of tomato juice every 30 miles (I didn't know salt caps existed, and couldn't handle any sports drink). Then I did take salt per instruction equaling 1S!cap/hr. Then stopped taking it, again, at races, almost at all (Bighorn 100 – 5 total). Then went into idea take 1/hr during a day and 1/3hr after sun goes down. I never cramp, whether with or without. I do have stomach problems, which get settled with 300mg Na average consumption/hr (if more than that – different kind of problem). p.s. my diet has somewhat less salt than "regular American", but surely not void of it. Joe, thanks again.

Great write-up, Q&A and place for thinking and open discussion! I just bought the book and am excited to read. Joe, you made an interesting comment to your reaction to salt at WS

"I reached into the hydration pack to find my mini-pouch of S-caps. I bit down. It tasted good.

With the next thirty minutes, two interesting things happened: My brain and legs returned to life, and my stomach felt much better."

I say that, because during my first ultra, 9-Trails in California. I was 27 miles in, the furthest I had ever really run, in the heat of the day and feeling nauseous and a little out of it mentally. The crew at the next AS gave me two Scaps! and very quickly I was more alert and my stomach was settled. I learned from the old school crew of the Karl King teachings that salts and stomachs had a nice balance and ever since I tend to take Scaps with me. I've realized that if I take one regularly (maybe every 90 min) I tend not to get nauseous as easily and if I take them when I am, my stomach rebounds fairly quickly, along with my mental capacity to function.

I am going to read the book to find out, but has there been any discussion as to thirst to quench a dry throat versus thirst to because of need/dehydration? I find that I have that battle, particularly out West. It's been hot and dry here all summer in Utah and some days I just drink because my throat feels like cotton, but I doubt I'm actually thirsty.

I don't see any mention of Cal-Mag. Calcium-Magnesium are sometimes the main ingredients in 'salt tablets'. The sodium level in some of the tablets is actually quite low. Is it possible that the cal-mag in these tablets is what is really at play?

Possibly. Supplements such as Hammer's "E-Caps" have a broad spectrum electrolyte with relatively less salt. I know little about the physiology of these electrolyte concentrations, as they were not addressed in this text.

Sodium- what if it has to do with chemistry inside the stomach, gastric emptying, etc. In your story above Joe, you noted that you had eaten a lot in the past hour (hour 5), but had no energy, but upon ingesting sodium, you suddenly felt better. Might this have been your stomach chemistry changing with the addition of salt and now the gut was absorbing everything?

A similar phenomenon has happened to a friend of mine in the past. He started with the leaders at Leadville, but at about the 5 hour mark, he reported that his stomach was sloshing around and no calories were getting in. He ate his first salt pill ever at Twin Lakes and he immediately absorbed all of his stomach contents. He instantly surged and felt solid through the end. He finished 2nd.

I have felt this happen myself, but never this drastically. Perhaps sodium encourages the gut to work better under times of stress.

1.) There is a difference between homeostasis and optimal performance. For homeostasis – staying level (or, at its core, alive), drinking to thirst is ALL you need to do. IF you are physiologically low on water, your brain will tell you to drink.

Optimal performance is different. What Dr Noakes advocates in his book is to FIRST drink to thirst – in various conditions – then gain a more specific idea of how much water that was, then (and truly only then) do you titrate that throughout the run. His research says that is 400-800ml/hr, across the board.

That said, for optimal race performance, don't wait until you're extremely thirsty: rather, know how much you need, and drink that (minimal) amount that will optimize performance without jeopardizing. Based on your calculations, you're getting a good idea of what your needs are.

2.) If you drink to thirst, you will not die of dehydration, nor are you in any danger of any other illness. Again, this myth is based on the "catastrophe model" (see Part I) — the idea that our bodies are incapable of fending off disaster, especially in an event where the intensity is SO low and SO prolonged, giving brain and body ample time to communicate.

My problem is I read the writings of experienced runners, like Horton and some other Woman that did The Worlds Indoor running Competition. I see that Horton says he urinated 23 times in 25 hours and this was okay. Then I read that this Women says she was peeing brown (maybe bloody) – also she said she "likes the feeling of almost having a heat stroke". Yes, she said it on her blog.

Anyhow, I just hope I and others find the right balance. To me the Sport Drink companies and Salt Pill companies are selling something just as this MD is selling something, for him it may be publish or perish. "buy Gatorade", "S-caps", "Drink to Thirst"

Congrats on your improved '12 WS performance. I suffered from weight gain and 141k CPK this year as WS. I am quite sure it was from over hydrating and sodium intake. Can you share what your CPK value was this year with you new nutrition/hydration philosophy?

I started this season back in Jan. Drinking too much and feeling like crap after long runs. I had been forcing fluids during and after runs. After reading this book, I've started drinking to thirst and feeling soooooo much better. My times have gotten better too! I do think that the salt thing is a little diff ? I now drink to thirst but take salt as needed, just seems to keep my stomach open for business when it comes to getting down Cals. Really good info and great to read what others experiences are.

With regards to salt, could there be something to the idea that you have trained your body for XX many years to take in salt during these conditions, and it adapted to that, and you simply haven't been at the new strategy of no salt long enough to adapt to it?

Good question. I think that's possible. I hear anecdotal reports of folks on a lower salt diet – who neither train or use salt consistently in races – who are able to complete 100M's competitively and effectively on <1g of dietary salt during that period.

It could be that since we drink way too much, we have to take salt because we are flushing it out.

I do agree with high salt being trained to be normal

What I have been wondering – Is one of the causes of being a heavy sweater because I general drink a fair amount day in and day out. (Not talking about beer here either) The body is an amazing thing and can compensate for many variables we throw at it.

I am mentally chewing on the info and need to take steps to digest it. In 16 days I have a 24 hour race – I am going to try and cut back on fluids and about 50% of s-cap intake.

Excellent point on "mouth feel" vs actual physiological thirst. Studies have been performed where those that simply swished flavored water (without swallowing) ran faster than a water control (or a non-drinking control) in short-distance (<marathon) running…

I wish I had read Waterlogged before Western States. I was quite aware of the issue of EAH; still, I am pretty sure I overhydrated, drinking too much Gu2O in an effort to keep a steady stream of calories coming. (I peed 23 times!) I finished, but much slower than I had anticipated. (Final sodium was 137, low, but not too bad.)

After WS I read Waterlogged (my pacer put me onto it). Since then I have run a marathon, a hilly 50K, and a hilly 50M. In all three, I followed Noakes' advice, specifically from the last chapter of his book: drink 600ml / hour, consuming 60g carbs / hour. That's conveniently one 20-oz. handheld, and 3 gels. I drank 1/6 bottle every 10 minutes, with half a gel from a gel flask. I used Hammer Gel, because it has minimal sodium (20mg per gel). I took no other electrolytes. I also started each race with 400ml + 40g carbs in my stomach.

I was happy with the results:

– In the marathon (flat), 10 days post-WS, I ran a very comfortable 3:07 (PR is 2:58).

– In the 50K, 10 days later, I ran a very comfortable race, beating my goal by 10 minutes, 1AG. Lots of quad-pounding downhill, but I was able to fly down the last long downhill, several miles. No cramps or anything approaching cramps.

– The 50M was tougher (White River), and I was pretty beat up towards the end, but I did manage to beat my goal time by 13 minutes, and my previous White River time by two hours. Again, no cramps, though I was on the edge a couple of times.

I was very fascinated to read about your experience with salt at WS, and Noakes' comments on salt and performance. Perhaps I might have gotten a boost late at White River with some salt. The previous time I ran White River, I was frozen solid with quad cramps at M37, until someone ran by and gave me a salt pill… within 30 seconds, I was running again. That was not enough to convince me that salt has anything to do with cramps, but I'm looking back now with a new perspective.

I was planning on following the same fueling strategy for Cascade Crest, but there is no crew access or drop bags after M73, so that means muling an awful lot of gel if I want to stick to that… looks like solid food it will be. And I will have to reconsider salt.

Right up front I do need to declare a something of a commercial interest here; I have recently started a company (www.myh2pro.com) doing sweat tests (for the amount of sodium in an athlete's sweat) and a range of electrolyte drinks in tablet format that give very low to very high levels of sodium per litre.

This was born out of experiences I had as an athlete competing in Ironman triathlons and Ultra marathons about 6-8 years ago. I would routinely perform well (top 5% of the field) in cool conditions but struggle in the heat with dead legs, general fatigue and lethargy (despite increasing water/calorie intake) and cramps.

I learnt (via trawling the web and some trial and error) that taking salt tablets might help and started doing so – as a direct result my performances improved dramatically back up to where I thought they should be (and were in cool conditions).

I got my sweat sodium analysed in a lab and found it to be very high (circa 80mmol/l) and via a friend who is a medic got hold of a machine and started testing other athletes. We have found a large range in sweat sodium loss between individuals (approx 18 to 86mmol/l in the athletes we have tested) and that generally those with higher sweat sodium losses do seem to benefit more from ingesting sodium at higher rates during extended exercise.

When I read Waterlogged recently I was massively impressed with most of it (and have been doing an 'experiment of one' with many aspects myself) but there were a few points that do not fit with my experiences – as some have also stated here:

Having sweat tested approaching 1000 athletes (mainly in UK) we've found this large variation in sweat sodium levels (18-86mmol) to be present yet the range reported in Waterlogged is much smaller (Page 111 – '…what is known is that both water and sodium are lost in sweat. But sweat has a low NaCl concentration usually between about 20 and 40 mmol/L…')

In our data there appears to be a statistically significant link between having higher sweat sodium losses and a higher incidence of cramping (we ask all sweat test candidates to rate their cramping episodes as never, rarely, sometimes or often when doing a sweat test).

We've also got mounting anecdotal evidence that cramping can often be stopped or prevented in a large proportion of cases with increased sodium intake.

Whilst much of the data/evidence we have is from pilot studies and anecdotal sources it is mounting up daily as we test more athletes and they tweak their sodium intake regimes accordingly. The results from the research that Dr Noakes points out from New Zealand tallies well with what we're seeing 'on the ground' with athletes too and it is interesting to hear that he is open to the idea that sodium 'may' have performance benefits, even if we can't precisely put our finger on exactly why as yet.

Based on personal experience and the data from our testing and feedback from athletes I definitely feel that an individual's rate of sodium loss (in sweat) is influential in driving the sodium requirement they have during prolonged exercise and that because this variation is rarely measured/known it could go a long way in explaining why some athletes seem to need salt/sodium supplementation (or benefit from it markedly) whilst others don't…

Anyway, I thought I would add this information to the thread in case it is of interest.

I really like well thought out, well written pieces (Joe) and responses (Andy) like this. I like how you address the various nuances of this subject. I like how they clearly state findings from a scientific/clinical approach vs. anecdotal. I like how they sometimes say, "we're not sure or we don't know".

It is interesting how there seems to be two separate issues. Issue #1 is the "I feel like crap but don't have any muscle issues". Issue #2 is the "I have good energy (my brain feels good) but my muscles seized up on me."

I pre-mix that into flasks. Actually its 60g malto, 30g fructo, x2. I can't explain how it works, you put that in a glass, add some warm water, and eventually it gets liquid enough to get-into/squeeze-out-of a plastic flask. It's easier with less carbs/more water.

Thank you Joe for sharing your findings. Great article! I'm just curious about the S-caps. I noticed that they do have potassium in addition to salt. Would potassium make the difference or are they in negligible amounts that they don't? I was just curious since the focus is on the salt content when it does have the potassium in it.

Great write up, Joe! Does Noakes say anything about gender differences? Many women that I have spoken with have admitted that use of a modest amount of electrolytes was a total game-changer in terms of their ability to run well in the heat.

I have read the book "Waterlogged". I have always drank a lot during running but still ended up losing weight. Drank less when in a hurry as in a race as opposed to a training run. But it is a mistake to be in a hurry and not take enough time to take care of your needs in the 100. However I do not usually drink water if I don't want it. I sometimes desired and drank Pepsi or something when I didn't particularly want water. Other times I was so thirsty that I had to have water before even Pepsi appealed to me. I liked Exceed when they still had that. I used to mix the powder to what tasted good rather than following the instructions.

I think it is an advantage to have good tasting water during a running event such as from a favorite well or even a bottled brand you like.Also use to mix your electrolyte/sweet beverage powder. The municipal water where I live tastes rather poor and I think contributes to nausea,even a while after you have drank it. I have not seen that issue addressed in the running press. I do realize that if you get thirsty enough you will generally eventually drink bad water such as even from a mud puddle if you had to run too far after missing a water stop.

I don't think I personally have to restrict my water intake even after reading that book,the worst that might happen is to have to pee urgently. I do think it is ridiculous to keep drinking at every water stop in a marathon or 10K when you are not thirsty to the point that you either gain weight or have to hit the bushes every 10 minutes. But I have been very thirsty and not had water immediately at hand,I don't want to get into that if I can possibly avoid it. Not fun.Would rather be just a little "waterlogged" instead.

I didn't seem to need extra salt/sodium during the runs such as O.D. but then the drinks had some salt,even Coke does I believe. But to each his/her own and I don't think it would hurt much to try a salt pill especially if they taste good. Also a possibility is a piece of cheese. I might have sampled a milk or chocolate milk a few times-too much could cause indigestion but one little box shouldn't and the chocolate milk especially I think has a little salt in it.

YES, this was going to be my question exactly. I keep reading SALT/sodium – so is all this talk about JUST sodium, or the mix that many of us are taking which is salt+potas+mag+calc+etc as found in Saltstick pills? Can someone please clarify or share a ref link w/ any explanations.

Memories from chemistry/biology lead me to thinking the other minerals need to be replaced as they are sweat out too, not just the singular focus of salt. Any insight is appreciated.

Again, I have to reiterate one of the fundamental points laid out by Dr Noakes and his research:

There is NO data to suggest that we must "replace lost things" DURING exercise. NONE.

The rationale for inclusion of a broad-spectrum electrolyte comes ONLY from analyzing what is lost in sweat…not what has been found to be beneficial/performance-enhancing during exercise.

An interesting analogy is fat: it is well-known that significant fat is burned in long-duration, low-intensity exercise. But you don't see anyone supplementing with ingestible fat sources DURING exercise…

I used to take 1-2 S-caps/hour. Last race (cascade crest) I took about 6 S-caps total in the first third of the race, mainly because I had them and felt a bit guilty (I'm being serious) about not following the old mantra. But they didn't change anything. The second half I took none, although I admittedly did eat normal food that probably had a high salt content, like toasted cheese, PB&J, potatoes w/salt (because they simply taste better that way), gels, etc. Drank to thirst. It all worked out fine. Same with white river 50, where I took none.

For my next 100 race, I'll probably carry 10 or so S-caps because they weigh nothing, but not take any. It's not an A race, so I'm looking forward to the experiment. But so far, I'm starting to buy the argument that taking regular electrolytes doesn't do much. Of course, they don't cost or weigh much of anything, so I suppose it doesn't matter that much, whereas water intake does.

One thing to throw in there though: if you read the comments from those who came before on blistering (http://www.ultrunr.com/footcare.html), there are lots of comments about proper hydration and electrolyte intake having an impact on blistering. Just sayin'…..

You say "In our data there appears to be a statistically significant link between having higher sweat sodium losses and a higher incidence of cramping".

Being well versed in statistics, I am curious as to what you mean by this statement- either your data are statistically significant via some test and accepted standard or they are not. Could you clarify. I realize that you may be referring to interim results but I will suggest that such references are dubious without peer review. If your data are statistically significant then I suggest you publish.

More importantly, what sort of mechanism have you proposed to explain such results?

Thanks for the comments. I've spoken with Dr Raj Jutley (our CMO) about the statistics and the numbers behind them and details are below. I'm not as well versed in statistics as either you or he but let me know if this answers your query and I can always ask for more detail if needed, or put the 2 of you in touch?

We took 342 sweat tests (most of our early subjects, all athletes, mostly endurance athletes) and conducted simultaneous questionnaires.

Subjects were asked if about their cramping experiencing during exercise and whether they cramped NEVER / RARELY / OFTEN or ALWAYS

As regards publishing – Dr Jutley says he does intend to publish but has not done so yet due to time pressures and other work commitments (his position with us is not full time).

In terms of the exact mechanism behind this….we are not sure at this stage. However as I said in my original post we are seeing what we believe to be a link between the level sodium loss and the incidence of cramping and/or poor performance in longer and hotter events. We're certainly not saying it is black and white, or indeed the same for all individuals, however there does appear to be a trend worth looking at more closely. We'll be continuing to investigate this further with research where we can and also in collating anecdotal feedback from athletes we test.

My own feeling is that we perhaps all have something of a threshold of tolerance for sodium loss, below which performance is negatively affected (sometimes with symptoms such as cramping, sometimes not). However many factors influence this including rate of sodium loss in sweat, level of sodium intake (habitually in normal diet and acutely during races), ability to tap into any proposed sodium stores in the body, variances in the threshold level between people, level of fluid intake and so on.

Whatever the mechanism I am firmly of the belief that the whole hydration/electrolyte balance and replacement equation needs to be very individualised and than a mix of scientific 'knowledge' and trial and error is the best way for an individual to get a handle on what works best for them.

Could it be that your stomach shutdown after the two PBJs and candy bar? That's a lot within 7 miles. Could be why you felt down and it was the time it took to digest them that brought you back not the salt. I find that when I eat too much PBJ at one time I get sluggish until I fully digest it and then it gives me a great kick of energy.

The stimulus effect Noakes talks about as a possible alternative explanation for performance improvement suggests that tasting the salt as you ingest it might send a stronger and quicker signal to the brain. You might not even have to swallow it!

Thanks for the post. I never felt nauseous. My stomach (thankfully) is awesome almost all the time…except when I'd given it nothing but gels for the first 30+ miles. If anything, the real food made it feel better. What the food *didn't do* was reverse my general energy malaise.

Per the "taste", you're dead-on. This was the theory behind the "pickle juice" study he mentioned in the interview: that only through a taste/neuro connection could something be so fast-acting.

Next data point: did Chimera 2012 (100 miles, 21,500 gain/loss) in November. I brought 5 S-caps with me 'just in case.' Used none of them. Ran a reasonably fast 20:33. Zero issues with cramping. Zero. Obviously, aid station food has some salt in it, but wasn't seeking out the salty stuff in particular.

It may matter person to person, but I've found _FOR ME_ over the limited years I've been doing this, that when I cramp it's because I'm simply overextending myself and pushing too hard (and it usually happens around 4-5 hours in, always in a 50 miler which is short enough that I can be dumb enough to overextend that early). Initially, when I'd start to cramp in these situations, I'd slow down, pop some MORE S-caps (because I was doing 1-2/hour already), and slowly the cramping would go away. But note that I was also slowing down! Now, I just decrease the intensity a hair; doesn't take much, and the cramping is averted. For me, salt appears to have nothing to do with it.

Will keep trying this out next year. But, will also likely always carry 5 or so S-caps with me… just in case. The placebo effect is strong!

What I would speculate is in the "over-extending", the issue might be a biomechanical one (muscle inefficiency) rather than physiological (energy systems, eletroyltes, etc). By slowing down, your mechanics return to their more efficient state… Food for thought…

There are a lot of variables here. Take sweat rates and sodium concentration in sweat. There is considerable variation due to genetics, and considerable variation due to heat training. Furthermore, those on a high salt diet will excrete more sodium, and those on a low salt diet will conserve it. That is why no formula can tell you how much electrolyte to take at a given race.

I find when I'm low on sodium, I am thirsty and I pee a lot, every 20 minutes. Taking sodium fixes that. Also, I must take sodium right around the end of a hundred miler, or I'll get sick right afterwards. So we all have to be aware of our body's reactions to varying amounts of water and sodium under varying conditions — everyone is different.

Certainly not while warm weather trail running, but most cold weather expeditions and Arctic explorers carry sticks of butter or some sort of solidified fat and eat a large percentage of that as part of their diet, I want to say at least %30 of calories from it while expending many calories on cold expeditions.

I believe the diet of northern native peoples (Eskimo-Aleut, Inuit, etc.) has been shown historically to eat a (relatively) higher percentage of fatty foods. If this shows anything, I'd think it'd be that humans are a highly adaptable species and can figure out what works best for them in varied environments.

It's worth noting that a major area of focus recently for Dr Noakes is the benefits of a high-fat, low-carbohydrate (sugar) diet – for both the general population and athletes.

However, he's noted in his previous works (Lore of Running, most updated edition – 2003?) that the primary role of sugar is for brain/liver glucose levels – not the muscle. This would align with the notion that fatty fuels are usable for prolonged exercise, so long as it is sufficiently low-intensity.